01 · Independence benchmark
Multiply the leg probabilities. Then name the assumption.
For leg probabilities expressed from 0 to 1, the benchmark is:
It answers a narrow question: What would the combined chance be if the selected legs were independent? It does not decide whether the legs are independent, or whether a venue is currently prepared to quote the combination.
02 · Worked examples
A few clean numbers make the compounding visible.
| Leg probabilities | Combined benchmark | Approximate 1 in X |
|---|---|---|
| 90% × 90% × 90% | 72.9% | 1 in 1.37 |
| 90% × 90% × 90% × 90% × 90% | 59.0% | 1 in 1.69 |
| 90% repeated 10 times | 34.9% | 1 in 2.87 |
| 80% × 80% | 64.0% | 1 in 1.56 |
| 80% repeated 5 times | 32.8% | 1 in 3.05 |
“1 in X” is simply 1 divided by the combined benchmark, rounded for readability. It is a different way to express the same assumed probability—not a claim about what will happen.
03 · The assumption that bites
Related legs are not automatically independent.
If the same game, team, player, weather event, or news event affects multiple legs, those outcomes may be related. A calculation that pretends otherwise can create false precision. The relationship might increase or decrease a true combined likelihood; this guide does not invent a correlation coefficient for it.
- Treat shared-event or shared-subject legs as a correlation warning, not as proof of a precise adjustment.
- Keep each leg’s source and timestamp beside any probability used in a calculation.
- Separate Bookie’s input math from the venue’s current quote and from your own judgment.
04 · A necessary boundary
Probability does not manufacture liquidity.
A Combo calculation can help you understand how an all-legs-must-win condition compounds. It cannot tell a counterparty to quote the request, reveal an account-scoped offer, or promise that an exit will exist later. Use the current venue quote only when the venue actually provides one.